Immobilization of Thermoalkalophilic Lipase from Bacillus atrophaeus FSHM2 on Amine-Modified Graphene Oxide Nanostructures: Statistical Optimization and Its Application for Pentyl Valerate Synthesis.

Abstract

Synthesis of (3-aminopropyl) triethoxysilane (APTES)-functionalized graphene oxide (GO) nanosheets, statistical optimization of conditions for immobilization of Bacillus atrophaeus lipase (BaL) on as-synthesized support, and application of the immobilized BaL for esterification of valeric acid were carried out in this investigation. The optimum specific activity of the immobilized BaL (81.60 ± 0.28Umg-1) was achieved at 3mgmL-1 of GO-NH2, 50mM of phosphate buffer, pH 7.0, 60min sonication time, 100mM glutaraldehyde, 25UmL-1 of enzyme, and 8h immobilization time at 4°C. The immobilized BaL retained about 90% of its initial activity after 10days of storage. Moreover, about 70% of the initial activity of the immobilized BaL was retained after 10cycles of application. The results of esterification studies exhibited that maximum pentyl valerate synthesis using the free BaL (34.5%) and the immobilized BaL (92.7%) occurred in the organic solvent medium (xylene) after 48h of incubation at 60°C.